Jannik Sinner will face Alexander Zverev in the Australian Open final after the defending champion saw off Ben Shelton in straight sets in Melbourne.

World number one Sinner recorded a 7-6 (7-2) 6-2 6-2 victory over American Shelton on Rod Laver Arena - the stage where he claimed his first major title 12 months ago.

Earlier on Friday, an injured Novak Djokovic was forced to retire after losing the first set against world number two Zverev.

Zverev, still bidding for a first major title after losing his previous two finals, now faces a daunting task against the in-form Sinner in Sunday's final.

"We've had some tough matches in the past. Anything can happen," said Sinner, who has lost four of his six meetings with Zverev.

The women's final between two-time defending champion Aryna Sabalenka and Madison Keys takes place on Saturday.

Reigning US Open champion Sinner is the youngest man to reach multiple Australian Open finals since Jim Courier in 1993.

Italy's Sinner has been near-unbeatable in the past 12 months and will go into the final on a 20-match winning streak, having not lost a match since 2 October last year.

Shelton, bidding to reach his first major final, made a confident start by breaking Sinner in the first game of the match - but that was an advantage the 21st seed surrendered three games later after a series of unforced errors.

Shelton, 22, broke again for a 6-5 lead and served for the set but squandered two set points as Sinner dug in to force a tie-break.

Sinner took control from then on, reeling off five straight points to close out the breaker before quickly going up a double break of serve in the second.

The daunting prospect of needing to come back from two sets down against the top seed did not discourage Shelton from entertaining and engaging the crowd.

The American reset admirably to force three break points early in the third set. But, after they went untaken, Sinner struck what proved to be the decisive blow in game five to extinguish Shelton's hopes of an unlikely fightback.

Despite appearing to limp following an awkward landing, Sinner closed out five straight games to secure victory in two hours 36 minutes.

"There was a lot of tension and I had some slight cramps," Sinner said afterwards.

"These matches can go very long. Three sets in two-and-a-half hours is quite some time, so I'm happy to finish it in three."

Sinner's Australian Open title defence comes against the backdrop of his ongoing doping case, which will be heard at the Court of Arbitration for Sport from 16 April, with the World Anti-Doping Agency seeking a ban of between one and two years.